{
  "id": "1909.10291",
  "version": "v1",
  "published": "2019-09-23T11:20:25.000Z",
  "updated": "2019-09-23T11:20:25.000Z",
  "title": "The evolution of pitch angles of spiral arms",
  "authors": [
    "J. E. Pringle",
    "C. L. Dobbs"
  ],
  "comment": "4 pages, 3 figures, accepted for publication in MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "In spiral galaxies, the pitch angle, $\\alpha$, of the spiral arms is often proposed as a discriminator between theories for the formation of the spiral structure. In Lin-Shu density wave theory, $\\alpha$ stays constant in time, being simply a property of the underlying galaxy. In other theories (e.g tidal interaction, self-gravity) it is expected that the arms wind up in time, so that to a first approximation $\\cot \\alpha \\propto t$. For these theories, it would be expected that a sample of galaxies observed at random times should show a uniform distribution of $\\cot \\alpha$. We show that a recent set of measurements of spiral pitch angles (Yu & Ho 2018) is broadly consistent with this expectation.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-09-23T11:20:25.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "spiral arms",
      "lin-shu density wave theory",
      "spiral pitch angles",
      "arms wind",
      "spiral structure"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 4,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}